JP5390979B2 - Motor unit for electric power steering and electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering motor unit and an electric power steering apparatus including the same.

  An electric power steering system EPS (Electric Power-Steering System) mounted on a vehicle appropriately controls a torque sensor for detecting steering torque and assist torque applied to the steering torque by controlling the output of the electric motor according to the torque sensor signal. An electric power steering motor unit (hereinafter, referred to as a motor unit) to be adjusted to a gearbox, and a gear box that generates an output torque obtained by adding an assist torque to a steering torque. Such an electric power steering device drives an electric motor in accordance with a signal from a torque sensor, and gives an assist torque according to a driver's intention to operate, thereby making the operability of a steering handle provided in the vehicle comfortable. It is.

  The motor unit includes a full bridge circuit that includes a power semiconductor element and controls the electric motor by a PWM (Power Width Modulation) method, and a control board that outputs a control signal to the power semiconductor element and adjusts the output power of the full bridge circuit. An arranged motor control device is provided. Since such a motor control device includes a power semiconductor element such as a full bridge circuit, a heat radiator such as a heat sink is required. However, in order to fully demonstrate the function of the radiator, the position of the radiator of the motor control device is selected. Therefore, the motor controller is arranged at a position away from the housing of the motor unit. It was common to be done. In such a case, since the electric motor built in the motor unit and the motor control device arranged independently of the motor unit are electrically connected by the harness, the voltage drop caused by the harness and the complicated assembly work. Along with these problems, it has been pointed out that the production cost will rise.

  Therefore, various studies for avoiding these problems have been made in recent electric power steering devices. An example is introduced below.

  Japanese Patent Laying-Open No. 2004-320835 (Patent Document 1) introduces an electro-hydraulic power steering device (electric power steering device in claims). Such an electrohydraulic power steering apparatus includes a motor unit and a control unit (the configuration constitutes an electric power steering motor unit in the claims), and the motor unit is one surface of the control unit. Fixed to. The control device section includes a housing composed of two housing parts. The housing controls a power semiconductor element that supplies appropriate electric power to the motor, a filter circuit that reduces noise of input power, and drive control of the power semiconductor element. A control board is accommodated. In addition, a bearing is provided inside the housing, and the output shaft of the motor unit is pivotally supported. On the other surface of the control unit (housing), the output shaft protrudes to the outside of the housing. The output shaft is connected to the hydraulic device.

JP 2004-320835 A

  However, in the technique according to Patent Document 1, since the housing includes all the components such as the control board and the power semiconductor elements constituting the filter circuit, the full bridge circuit, etc., the housing is very large. The Accordingly, since the bearing must be attached to such a large housing, there arises a problem that the assembling work is complicated, and further, the fixing jig in the production line is enlarged.

  Also, since the bearing is fixed inside the housing, when replacing or repairing the bearing, the work must be performed after the housing containing the control board or the like is disassembled. There is a problem that the work becomes complicated. Further, in such a housing, the bearing cannot be visually observed only by being removed from the gear box of the electric power steering apparatus, and therefore it is not possible to easily determine whether or not the cause of the failure is the bearing of the housing.

  In view of the above problems, an object of the present invention is to provide an electric power steering motor unit and an electric power steering device capable of realizing simplification of assembly work and simplification of bearing replacement work or repair work.

In order to solve the above problems, the present invention has the following configuration of an electric power steering motor unit. That is, an electric motor that generates a drive torque on the drive shaft in accordance with the rotation of the built-in rotor and a power semiconductor element that converts the input electric power and drives the electric motor. A power conversion unit that outputs drive power for power supply, a power element substrate on which the power semiconductor element is mounted, a motor side bracket that accommodates the power element substrate, and the drive shaft that is mounted on the motor side bracket. In a motor unit for electric power steering, comprising: a bearing that is pivotally supported; and a control board that is provided independently of the motor side bracket and outputs a control signal of the power semiconductor element.
The bearing holder for housing the bearing is formed on a contact surface with the gear box structure portion of the motor side bracket, and the bearing is mounted from the contact surface with the gear box structure portion toward the motor side. And
The power element substrate is laminated on the motor side bracket via an adhesive resin or grease.
The motor unit for electric power steering, wherein the adhesive resin or the grease has a higher elastic coefficient than the material of the motor side bracket and the material of the power element substrate.

Preferably, a power distribution unit including an electric circuit for relaying input power and an electric circuit for insertion inserted in the electric circuit is provided between the control board and the power element board.

Preferably, the power element substrate includes an insulating metal ceramic substrate and a printed wiring laminated on the metal ceramic substrate.

Preferably, the metal ceramic substrate is made of aluminum nitride or alumina.

In the present invention, the following electric power steering apparatus may be configured. That is, the electric power steering motor unit described above and a gear box that adds the assist torque to the steering torque according to the turning operation of the steering handle are provided.

  According to the motor unit for electric power steering according to the present invention, the motor-side bracket to which the bearing is attached is miniaturized, so that the work for attaching the bearing is facilitated. Further, since the motor side bracket is downsized, the entire apparatus of the motor unit for electric power steering is reduced, and the downsizing of the fixing jig in the production line can be realized.

  In addition, since the bearing attached to the motor side bracket is attached from the outside of the motor side bracket, the bearing can be removed without performing complicated disassembly work such as a control board.

  Furthermore, according to the electric power steering device according to the present invention, it is possible to visually check the state of the bearing just by removing the motor unit for electric power steering from the electric power steering device, thereby fixing to the motor side bracket. It is easy to determine the failure of the bearing.

The figure which shows the structure of the vehicle carrying the electric power steering device. The figure which shows the structure of the electric power steering apparatus which concerns on embodiment. The figure which shows the internal structure of the electric power steering apparatus which concerns on embodiment. 1 shows a circuit configuration of an electric power steering apparatus according to an embodiment. The figure which shows the structure of the motor unit for electric power steering which concerns on this Embodiment. Sectional drawing of the motor unit for electric power steering which concerns on this Embodiment. The figure which shows the laminated structure of the board | substrate for power elements which concerns on this Embodiment. The figure which shows the relationship between the frequency of the voltage applied to printed wiring, and the impedance which arises in an insulating layer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the vehicle CAR includes a front wheel FT and a rear wheel RT provided in the chassis, and controls the yawing posture of the vehicle body by giving a steering angle to the front wheel FR. The front wheel FR is provided with a rack RCK and is steered according to the axial movement operation of the rack RCK. In recent years, vehicles employing so-called 4WS (4 Wheel Steering) in which front and rear wheels are steered according to the vehicle speed are also widely used.

  As shown in the figure, a vehicle CAR equipped with an electric power steering device (a driven device in claims) includes an in-vehicle battery BTT, a vehicle speed sensor VMU, an ECU 1 (Engine Control Unit / Electric Control Unit), a steering device HDM, and electric power. The steering device 200, an ignition relay IG, and a pinion gear box SGB are included.

  The in-vehicle battery BTT is composed of a rechargeable battery pack and outputs a voltage of about 12 to 24V. Such a battery pack does not ask the type of the battery.

  The vehicle speed sensor VMU converts information related to the vehicle speed into an electrical signal using a wheel rotation sensor or a sensor that detects a reflected wave from the road surface. In the vehicle CAR according to the present embodiment, information on the vehicle speed sensor VMU is transmitted to the ECU 1.

  The ECU is generally called an “engine control unit” for a vehicle equipped with an internal combustion engine, and is generally called an “electric control unit” for an electric vehicle. However, the present embodiment is not distinguished by these differences, and a desired signal is transmitted to the electric power steering apparatus 200 based on the speed information received from the vehicle speed VMU. In addition, the ECU 1 receives information from sensors installed in the vehicle and performs appropriate processing related to operation control of the vehicle CAR. In recent years, an ECU is provided in each sensor and can share information of each sensor with a CAN (Control Area Network). As will be described later, in the present embodiment, the electric power steering unit 100 is also equipped with an ECU for controlling the device.

  The handle device HDM is provided on the driver seat and transmits a steering torque according to the driver's steering intention to the electric power steering device 200. Further, the handle device HDM is provided with an ignition key, and when the ignition key is rotated, the ignition relay IG is switched to the ON state. In the case of an internal combustion engine, the cell motor is driven, and the electric vehicle In such a case, the control circuit for the wheel motor or the control circuit for another device is activated to switch to the standby state.

  As shown in the figure, the electric power steering apparatus 200 includes a torque sensor TS, a reduction gear box WGB, and an electric power steering motor unit 100 as main components, and the electric power steering motor unit (hereinafter referred to as a motor unit). Reference numeral 100 includes an ECU 2 and an electric motor EM as main components. The detailed configuration and operation of the electric power steering apparatus 200 and the motor unit 100 will be described later.

  In the pinion gear box SGB, the teeth formed on the rack RCK and the pinion gear fixed to the transmission shaft CSH are engaged with each other, and the rotational motion of the transmission shaft CSH is converted into the axial motion of the rack RCK. The transmission shaft CSH is appropriately provided with a universal joint to smoothly transmit the output torque applied from the electric power steering device 200 to the pinion gear box SGB.

  In the vehicle CAR having such a configuration, when the steering device HDM is steered by the driver, the ECU 2 drives the electric motor EM based on the signal from the torque sensor TS and the speed information from the ECU 1, thereby In the steering device 200, an assist torque is added to the steering torque by the driver, and an output torque corresponding to the steering intention of the driver is generated. At this time, in the vehicle CAR, the output torque gives an axial force to the rack RCK, so that a steering angle according to the steering intention of the driver is given to the front wheels FT regardless of the state of the load applied to the tires. This reduces the burden of handle operation by the user and improves operability.

  FIG. 2 shows a column type electric power steering apparatus according to the present embodiment. Such an electric power steering apparatus 200 is fixed to a main body portion including a shaft 210, a shaft case 220, a torque sensor housing portion 230, a signal terminal 240, and a gear box 250 (a reduction gear box WGB in FIG. 1). The motor unit 100 is comprised. Hereinafter, when the axial center of the shaft 210 is the axial direction, the side on which the gear box 250 in the axial direction is arranged is referred to as a rear side DR, and the opposite side of the rear side DR is referred to as a front side DF. Note that a pinion gear box PGW is connected to the front side DF via a transmission shaft CSH, and a handle device HDM is connected to the rear side DR.

  The shaft 210 forms a cylindrical bar, and includes a front side shaft 211 and a rear side shaft 212 and a torsion bar (not shown). The front shaft 211 has a male screw 211a and a spline 211b, and the rear shaft 212 also has a spline. Further, when the steering torque is input from the handle device HMD, the shaft 210 is given a torsion angle corresponding to the steering torque to the torsion bar. Further, a substantially hollow sensor shaft is fixed to each of the front side shaft 211 and the rear side shaft 212. The sensor shaft is formed with a groove that changes the cross-sectional area of the abutting surface in the torsional direction, and causes relative movement in the axial rotation direction according to the torsion angle of the torsion bar, thereby changing the cross-sectional area of the abutting cross section. Note that the mechanism of the torsion bar and the sensor shaft are stored in the shaft case 220 and the torque sensor housing portion 230.

  In the torque sensor housing portion 230, the butting portion of the sensor shaft is disposed inside. Such a sensor shaft has a primary coil pivotally attached to one side and a secondary coil pivotally attached to the other (not shown). The primary coil and the secondary coil are connected to the signal terminal 240 and connected to the motor unit 100 via a signal cable (not shown). That is, when a voltage is applied to the primary coil and a torsion angle is generated in the torsion bar, a change in magnetic flux is generated by the sensor shaft in the secondary coil, so that the twist angle is indicated from the secondary coil side terminal of the signal terminal 240. The induced voltage is output to the motor unit 100.

  As shown in the figure, the gear box 250 is integrally formed with a gear side bracket 252, and the motor unit 100 is fixed using bolts and nuts B / N. The internal structure of the gear box 250 will be described with reference to FIG. This figure shows a cross-sectional view of the AA cross-section described in FIG. 2 observed in the direction of the arrow. In this gear box 250, a worm housing portion 251 and a flat worm housing portion 252 are integrally formed.

  The worm housing portion 251 includes an input shaft 253 that rotates in conjunction with the operation of the motor unit 100. The input shaft 253 is formed with a worm gear 253g and is rotatably supported by bearings 254a and 254b.

  The flat worm 252g is formed with teeth of the same module as the worm gear 253g and meshes with the worm gear 253g. The flat worm housing portion 252 has a rear side shaft 212 pivotally attached to the center thereof, and the rear side shaft 212 rotates in conjunction with the operation of the flat worm 252g.

  When a steering torque is applied to the rear side shaft 212, the gear box 250 outputs a signal from the torque sensor in response to the torsional deformation of the torsion bar, and requests the motor unit 100 to output the driving torque. When a driving torque is output from the motor unit 100, the motor unit 100 and the worm gear 253g are rotated, and an assist force is applied to the flat worm 252g. Such assist force applies an assist force to the front shaft 211 via the flat worm 252g, whereby the assist torque is applied to the steering torque from the operator at the front shaft 211 of the gear box 250, thereby An appropriate output torque is generated.

  FIG. 4 shows a circuit configuration of the motor unit 100. In the figure, the configuration of the torque sensor TS is shown for convenience. As shown in the figure, the circuit configuration of the motor unit 100 includes an electric motor EM, a full bridge circuit constituting the power conversion unit 175, a control circuit 151 mounted on a control board, and an electric circuit. Appropriate electrical elements are provided as necessary.

  The electric motor EM is connected to the full bridge circuit via the relay circuit 180. The electric motor EM is applied with driving power from a full bridge circuit according to the operation of the relay circuit 180. The relay circuit 180 is controlled by the central processing circuit 151b and regulates permission / non-permission of the driving power output to the electric motor EM. That is, the electric motor EM is driven by the full bridge circuit when the relay circuit 180 is in the ON state, and the driving power from the full bridge circuit is cut off when the relay circuit 180 is in the OFF state.

  The full bridge circuit 175 (power conversion unit in the claims) includes power semiconductor elements 175a to 175d, and an output line is provided in each inverter unit. One of the output lines is connected to the terminal Tm1 via the relay circuit 180, and the other is connected to the terminal Tm2. As the power semiconductor elements 175a to 175d, MOSFETs or IGBTs having gate terminals are used. The power semiconductor elements 175a to 175d are appropriately provided with a ceramic capacitor, a Zener diode, and the like that protect the gate terminal. The power semiconductor elements 175a to 175d are heated by the passing current when a control signal is input to the gate terminal. In the present embodiment, the voltage value by the DC power is boosted to about 50V. Therefore, the amount of heat corresponding to this is generated in the power semiconductor element. Such a full bridge circuit converts the input DC power to output the driving power and supplies the driving power to the electric motor EM as described above. The power conversion unit in the claims is not limited to a full bridge circuit, and may be, for example, an inverter circuit. In addition, the power conversion unit performs power conversion using the power semiconductor element described above. I just need it.

  The power semiconductor element 175k is connected to an electric circuit that relays the input electric circuit. The power semiconductor element 175k is driven in accordance with a control signal from the drive circuit 151d. In some cases, the input power applied to the power supply terminal Vb is relayed to the filter circuit 144. In other situations, the input power to the filter circuit is used. Shut off the supply.

  The control circuit 151 is provided in a state that is physically independent from the full bridge circuit, and is installed at a position that is not affected by the heat generated in the full bridge circuit. As shown in the figure, the control circuit 151 includes a torque sensor detection circuit 151a, a central processing circuit 151b, an operation monitoring circuit 151c, a drive circuit 151d, a thermal detection circuit 151e, an overcurrent detection circuit 151f, and a CAN communication circuit. The torque sensor detection circuit 151a detects a potential difference generated between both coils of the torque sensor TS and outputs it to the central processing circuit 151b. The CAN communication circuit receives speed information from the ECU and communicates necessary information bidirectionally. The drive circuit 151d outputs control signals for driving the power semiconductor elements 175a to 175d and 175k. The thermal detection circuit 151e and the overcurrent detection circuit 151f receive signals from the thermistor 175e and the shunt resistor 175f, and output a warning signal to the central processing circuit 151b when the respective reference values are exceeded. The central processing circuit 151b outputs a control signal based on the signal of the torque sensor TS and the speed information. Such control signals drive the power semiconductor elements 175a to 175d, 175k, respectively. The central processing circuit 151b is provided with a plurality of fail safe functions. For example, when a signal indicating an abnormal state is input from the thermal detection circuit 151e or the overcurrent detection circuit 151f, the central processing circuit 151b stops outputting the control signal and stops driving the electric motor EM. In addition, an operation monitoring circuit 151c is connected to the central processing circuit 151b so that bidirectional communication is possible. The operation monitoring circuit 151c executes the same arithmetic processing as the central processing circuit 151b, and outputs the processing result to the central processing circuit 151b at every predetermined timing. At this time, the central processing circuit 151b outputs a control signal only when its own processing result and the processing result from the operation monitoring circuit 151c match, and when both processing results do not match, the central processing circuit 151b outputs the control signal. Stop output. That is, if a difference occurs in the processing result of the operation monitoring circuit 151c, the central processing circuit 151b determines that an error has occurred in its processing result and stops the operation of the electric motor EM. The torque sensor detection circuit 151a, the drive circuit 151d, the thermal detection circuit 151e, the overcurrent detection circuit 151f, the CAN communication circuit, etc. are configured by appropriate ICs, and the central processing circuit 151b and the operation monitoring circuit 151c are the CPU and others. It is composed of a microcomputer and DSP having a memory circuit and the like. In other words, all the electrical elements configured as the control circuit 115 are driven by weak electric power, and do not require high power as in a power semiconductor element.

  In the present embodiment, the circuit for electric circuit described above includes a filter circuit 144 and a relay circuit 180. The electric circuit connects the power supply line 177a from the power supply terminal Vb to which the DC power is applied to the full bridge circuit, the power supply line 177b from the full bridge circuit to the ground terminal GND, and the full bridge circuit and the electric motor EM. Output lines 177c and 177d to be included.

  The filter circuit 144 is inserted in the electric circuit 177a from the terminal Vb to which DC power is input to the full bridge circuit. The filter circuit 144 is appropriately provided with electrical elements such as a capacitor, a reactor, and a resistor.

  Note that the circuit configuration is satisfied if at least one of the relay circuit 180 and the filter circuit 144 exists. For example, even when there is no filter circuit 144, an electric circuit is formed by the relay circuit 180. When only the filter circuit 144 exists, the electric circuit is formed by such a circuit. To do. That is, the circuit for the electric circuit indicates a circuit connected to the electric circuits 177a to 177d as illustrated.

  5 to 7 show the configuration of the motor unit 100 according to the present embodiment. As shown in the figure, the motor unit 100 includes an electric motor EM, an inner bottom surface 120, a drive shaft 114, a power element substrate 170, a power distribution unit 140, and a control device 150 incorporating a control substrate. In the following description, the arrow direction DH in the figure is the heat dissipation direction, and the arrow direction DM is the motor direction.

  The electric motor EM uses a brush motor in the present embodiment, and specifically includes a rotor 111a, a permanent magnet 111e, a motor cover 160, a commutator 111c, and a brush assembly 111b. When the coil is wound inside the slit and the driving power is applied from the power conversion unit 175, the rotor 111a changes the state of the magnetic flux inside the rotor 111a. The motor cover 160 is a substantially cylindrical body, and accommodates the rotor 111a therein. In the motor cover 160, permanent magnets are arranged on the inner wall with alternating polarities. The commutator 111c is fixed to the rotor 111a, arranges conductor regions and insulating regions alternately on the cylindrical surface, and reverses the polarity of current for each region. The conduction region is electrically connected to the coil of the rotor 111a. As shown in the figure, the brush assembly 111b has a plurality of brush elements 112 arranged therein. The casing of the brush assembly 111b is formed of an insulating material, and wiring that is electrically connected to the brush element 112 is integrally formed.

  As shown in FIG. 6, when the electric motor EM is assembled, the contact surfaces of the brush elements 112 and the surface of the commutator 111c are in contact with each other. Therefore, when driving power is applied to the brush element 112, the rotor 111a rotates due to the magnetic force generated in the coil, and the commutator 111c also rotates accordingly. At this time, in the rotor 111a, the current flowing through the coil is commutated by the commutator 111c, and the rotation operation of the rotor 111a is maintained. Such an electric motor EM generates a drive torque on the drive shaft 114 in accordance with the turning operation of the built-in rotor 111a.

  As shown in the figure, the drive shaft 114 is fixed to the rotor 111a, and outputs a drive torque when the rotor 111a is driven. One end of the drive shaft 114 is supported by a bearing mechanism 162 in the motor direction DM, and the other end (heat radiation side DH) is supported by a bearing BR described later. A male-side spline 114a is formed on the heat dissipation side DH of the drive shaft 114, and is connected to the input shaft 253 via a socket SC in which a female-side spline is formed.

  The power element substrate 170 is mounted with a power converter 175, that is, power semiconductor elements 175a to 175d, 175k. Further, a thermistor 175e and a shunt resistor 175f may be mounted. Such an element is arranged in the vicinity of the power semiconductor elements 175a to 175d, thereby exerting its function. Further, in this embodiment, the control vertical terminal 176 and the electric circuit vertical terminal 177 are appropriately arranged.

  The motor-side bracket 130 is a bottomed cylindrical body as shown in the figure, and a bracket portion 131 and a case fixing piece 132 are integrally formed. The bracket portion 131 is formed with a bolt hole 131a and is fixed by the gear side bracket 252 and the bolt nut B / N. The case fixing piece 132 is formed with a female screw tap 132a, and the motor case 160 is fixed by a screw. Further, the power element substrate 170 is accommodated in the motor side bracket 130, and the power element substrate 170 is laminated on the bottom surface of the motor side bracket 130. That is, the power element substrate 170 is disposed on the heat dissipation side DH of the drive shaft 114. Thus, when the motor unit 100 is fixed to the gear side bracket 252, the bottom surface of the motor side bracket 130 and the gear side bracket 252 come into contact with each other, and the amount of heat generated in the power semiconductor devices 175a to 175d and 175k changes the contact surface. Is effectively transmitted to the key box 250. The motor side bracket 130 is preferably made of a material having high heat transfer performance. The material having high heat transfer performance is preferably, for example, aluminum, copper, or an alloy thereof. Further, the present invention is not limited to this, and a metal material having iron as a base material may be used.

  In addition, a bearing holder BH is formed on the motor side bracket 130, and an outer ring of the bearing BR is attached to the bearing holder BH. The bearing BR is mounted by a method such as press fitting or shrink fitting. On the other hand, the inner ring of the bearing BR is fixed to the drive shaft 114 by press fitting or the like, whereby the drive shaft 114 is pivotally supported with respect to the motor side bracket. In this embodiment, the durability is improved by using the bearing BR as a bearing. However, the present invention is not limited to this, and a sliding bearing or the like may be employed.

  The bearing holder BH that accommodates the bearing BR is formed on the heat radiation side DH of the motor side bracket 130, and the bearing BR is inserted from the position of the heat radiation side DH to the motor side DM with respect to the power element substrate 170, The bearing holder BH is preferably mounted. Thereby, the opening part of a bearing holder is distribute | arranged to the outer peripheral surface side of the motor side bracket 130, and the bearing BR does not need to decompose | disassemble the circuit inside the motor side bracket 130, when performing replacement | exchange work or repair work. . Further, when the motor-side bracket 130 is removed from the gear box 250, the state of the bearing BR can be visually checked, and it is possible to easily determine whether or not the bearing BR is out of order.

  In this embodiment, since the bearing BR (which may be a slide bearing) is used, when the bearing is mounted on the motor side bracket 130, if the press fitting is performed, an impact is applied to the bottom of the motor side bracket 130. This may damage the power semiconductor element. Further, if shrink fitting is performed, there is a possibility that the power element substrate 170 is deformed by thermal stress and the functions of the bridge circuit and the like are impaired. Therefore, in order to avoid such a problem, the laminated structure of the motor side bracket 130 and the power element substrate 170 is preferably configured as follows.

  FIG. 7 shows the laminated structure of the power element substrate. First, with reference to Fig.7 (a), the board | substrate for power elements which comprises an epoxy layer is demonstrated. As shown in the figure, the power element substrate 170 includes a metal substrate 171a, an epoxy layer 172a, and a printed wiring 173a. Of these, the metal substrate 171a may be an aluminum plate, or may be a metal alloy having a high thermal conductivity. The epoxy layer 172a is formed by laminating an epoxy resin on the surface of the metal substrate 171a to form an insulating layer having a thickness t1. The printed wiring 173a is formed in an appropriate wiring pattern and is laminated on the epoxy layer 172a.

  A power semiconductor element 175 is stacked on the printed wiring 173a via a solder layer 174, and a bonding wire is appropriately connected to the power semiconductor element 175. The power semiconductor element 175 is supplied with electric power through the printed wiring 173a and the solder layer 174, and interrupts a current corresponding to the electric power according to an input signal.

  Further, the power element substrate 170 including the epoxy layer is laminated on the motor side bracket 130 via the heat dissipating grease 201. The heat dissipating grease 201 is made of a material having high thermal conductivity such as silicon, and transmits the amount of heat transmitted to the metal substrate 171 a to the motor side bracket 130. Since the heat dissipating grease 201 is a semi-fluid, it plays a role of reducing the impact applied to the motor side bracket 130 and protecting the power semiconductor element 175.

  In the power element substrate 170 having an epoxy layer, since the thermal resistance of the epoxy resin is high, the thermal resistance is reduced by reducing the thickness t1 of the epoxy layer 172a. By suppressing the thermal resistance as described above, the amount of heat generated in the power semiconductor element 175 is effectively transmitted to the motor side bracket 130.

  Next, with reference to FIG.7 (b), the board | substrate for power elements at the time of using a metal ceramic board | substrate is demonstrated. As shown in the figure, the power element substrate 170 is composed of a metal ceramic substrate 172b and a printed wiring 173b, and a copper plating layer 171b is laminated below the metal ceramic substrate 172b. Among these, for the metal ceramic substrate 172b, alumina, aluminum nitride, or the like is used, and in addition, a ceramic metal substrate having high thermal conductivity is used. The metal ceramic substrate 172b is a material for forming an insulating layer. However, since the thermal conductivity is high, the metal ceramic substrate 172b can be set to a thickness t2 (> t1) thicker than the thickness of the epoxy layer described above. . The printed wiring 173b is formed in an appropriate wiring pattern and is laminated on the metal ceramic substrate 173b.

  Similarly to the above, a power semiconductor element 175 is stacked on the printed wiring 173b via a solder layer 174, and a bonding wire is appropriately connected to the power semiconductor element 175.

  Further, a power element substrate 170 using a metal ceramic substrate is laminated on the motor side bracket 130 via a highly heat conductive adhesive 202. Such a high heat transfer adhesive 202 is made of a material having a high thermal conductivity such as a silicone resin like the heat dissipating grease. In addition, the adhesive 202 preferably has a larger elastic coefficient after solidification than the material of the motor side bracket 130 and the power element substrate (metal ceramic). Thereby, when the bearing BR is press-fitted into the motor side bracket 130, the impact applied to the power element substrate is alleviated, and the power semiconductor element 175 is protected. Even when the bearing BR is shrink-fitted, distortion due to thermal stress is alleviated by the adhesive 202, so that the function of the power element substrate 170 is protected.

  In the power element substrate 170 in FIG. 7B, since the thermal conductivity of the metal ceramic substrate is high, the thermal resistance of the metal ceramic substrate is hardly affected by the thickness t2 of the metal ceramic substrate. It is possible to keep the value low. Therefore, the amount of heat generated in the power semiconductor element 175 is effectively transmitted to the motor side bracket 130 while suppressing the influence of the thermal resistance due to the plate thickness t2 of the metal ceramic substrate.

  In such an insulating layer, one side is given a predetermined potential by the current of the printed wiring and the other side is connected to the ground, so that charges are charged at both ends, thereby generating a predetermined coupling capacitance. And since this coupling capacity takes a value inversely proportional to the interlayer distance of the insulating layer, the following problems occur.

  FIG. 8 shows frequency characteristics related to impedance generated in the insulating layer. In the figure, the frequency characteristic of the insulating layer by the epoxy layer is shown by a curve Crv1, and the frequency characteristic of the insulating layer by the metal ceramic substrate is shown by a curve Crv2. The frequency band f1 indicates the driving frequency of the power semiconductor element 175.

  In the power element substrate on which the epoxy resin is laminated, the thickness t1 of the epoxy resin is thin, so that the interlayer distance between the insulating layers is reduced and the coupling capacitance C1 is increased. The curve Crv1 shows that when the coupling capacitance C1 increases, the impedance decreases at the frequency f1 to be used, and the insulating function by the epoxy resin decreases. Therefore, in the power element substrate on which the epoxy resin is laminated, current leaks from the printed wiring 173a to the motor side bracket 130, and the operation of the power semiconductor element 175 becomes unstable.

  On the other hand, in the laminated structure of the power element substrate made of metal ceramic, the problem relating to the coupling capacitance is solved as follows by appropriately adjusting the thickness t2 of the insulating layer. That is, the plate thickness t2 of the metal ceramic substrate 172b has a low thermal resistance and can be made thicker than the plate thickness t1 of the epoxy resin. In this case, since the power element substrate using the metal ceramic substrate can secure an insulating layer having a sufficient thickness, the interlayer distance between the insulating layers becomes long, and the coupling capacitance C2 in this case becomes small. The curve Crv2 shows that when the coupling capacitance C2 is reduced, the impedance at the frequency f1 to be used is increased, and the insulating function by the metal ceramic is improved. Therefore, in the power element substrate using the metal ceramic substrate, the insulation between the printed wiring 173b and the motor side bracket 130 is ensured, and the operation of the power semiconductor element 175 is stabilized.

  As described above, when a metal ceramic substrate such as aluminum nitride or alumina is used as the power element substrate, the thermal resistance can be suppressed even if the thickness of the power element substrate is increased. In the power element substrate, it is possible to appropriately increase the thickness of the metal ceramic substrate serving as the insulating layer to reduce the coupling capacity. That is, in the power element substrate having such a configuration, the impedance of the insulation section increases as the coupling capacitance decreases, so that the insulation between the printed wiring and the motor side bracket is ensured. Stable operation of the electrical element mounted on the substrate is realized.

  Returning to FIG. 5 and FIG. 6, the configuration of the control device 150 and the power distribution unit 140 will be described.

  As shown in the figure, the control device 150 accommodates a control board 153, and the control board 153 is mounted with a weak electric element constituting the control circuit 151. Since the control board 153 is provided in a state independent of the power element board 170, the configuration of the heat dissipation mechanism in the control device 150 is omitted as much as possible, and the control board 153 and the control device 150 can be downsized. Further, since the configuration of the filter circuit and the like is also eliminated, the size of the control device 150 can also be reduced.

  As shown in FIG. 5, the power distribution unit 140 includes a power terminal 141, a control terminal group 142, an electric circuit terminal group 145, and an electric circuit. Among these, the power terminal 141 includes a terminal portion and an insulating connector structure, and the terminal portion is provided with terminals Vb, GND, and the like. The control terminal group 142 is electrically connected to terminals provided on the control board. When the control device 150 is connected to the power distribution unit 140, the control terminal group 142 has one end connected to the control board 153 via the control side terminal 152 and the other end connected to the control vertical terminal as shown in FIG. 176 is connected to the printed wiring of the power element substrate 170. Further, when the power distribution unit 140 and the brush assembly 111b are assembled to the motor-side bracket 130, one end of the electric circuit terminal group 145 is connected to the brush element 112 via the brush terminal 111d and the other end is connected to the electric circuit. It is connected to the printed wiring of the power element substrate 170 via the vertical terminal 177, thereby playing the role of the electric paths 177c and 177d. The circuit for electric circuit is a circuit inserted in the electric circuit, and the filter elements 144a and 144b and the relay circuit 180 are appropriately mounted on the circuit board. The filter element refers to a relatively large element such as an electrolytic capacitor, a film capacitor, or a coil. That is, the control board 153 can be further reduced in size by consolidating large electrical elements in the power distribution unit 140.

  The power distribution unit 140 is preferably disposed between the control board 153 and the power element board 170. As a result, the power distribution unit 140 distributes the high power to be relayed to the power semiconductor element and the weak power used by the control board 153, thereby making the control board 153 and the power element board 170 physically independent. It becomes possible. Further, since the power distribution unit 140 configures short-circuit electric paths 177a to 177b and the like by each terminal group without using a harness, the influence of parasitic inductance is reduced, and the element size of the filter circuit 144 can be reduced. It becomes possible. That is, in the power distribution unit 140, the housing of the power distribution unit is downsized as the filter circuit 144 is downsized.

  Further, since the power distribution unit 140 forms a physical distance between the control device 150 and the power element substrate 170, the amount of heat generated in the power element substrate 170 is difficult to be transmitted to the control substrate 153, and the control substrate 153. Makes it possible to output a control signal without malfunction under a favorable temperature environment. In addition, since the risk of emergency stop due to fail-safe is reduced, the electric power steering apparatus 200 can stably supply the assist torque.

  According to the motor unit 100 according to the present embodiment, the motor-side bracket 130 to which the bearing BR is attached is reduced in size, so that the attachment work of the bearing BR becomes easy. Moreover, since the motor side bracket 130 is reduced in size, the entire apparatus of the motor unit 100 is reduced, and the fixing jig in the production line can be reduced in size.

  In addition, since the bearing BR attached to the motor side bracket 130 is attached from the outside of the motor side bracket 130, the bearing BR can be removed without performing a complicated disassembly work of the motor unit 100.

  According to the electric power steering apparatus 200 according to the present embodiment, the state of the bearing BR can be visually observed only by removing the motor unit 100 from the electric power steering apparatus 200. Failure determination of the fixed bearing BR becomes easy.

DESCRIPTION OF SYMBOLS 100 Motor unit for electric power steering 200 Electric power steering apparatus EM Electric motor 175 Electric power conversion part 130 Motor side bracket 153 Control board

Claims (5)

An electric motor for generating a driving torque on a driving shaft in accordance with a turning operation of a built-in rotor, and a power semiconductor element for converting the input electric power to drive the electric motor A power conversion unit that outputs driving power, a power element substrate on which the power semiconductor element is mounted, a motor side bracket that accommodates the power element substrate, and the motor side bracket that is mounted on the motor side bracket rotate the driving shaft. A motor unit for electric power steering , comprising: a bearing that freely supports a shaft; and a control board that is provided independently of the motor side bracket and outputs a control signal of the power semiconductor element .
The bearing holder for housing the bearing is formed on a contact surface with the gear box structure portion of the motor side bracket, and the bearing is mounted from the contact surface with the gear box structure portion toward the motor side. And
The power element substrate is laminated on the motor side bracket via an adhesive resin or grease.
The motor unit for electric power steering, wherein the adhesive resin or the grease has a higher elastic coefficient than the material of the motor side bracket and the material of the power element substrate. Between said power element board and the control board, to claim 1, characterized in that it comprises a distribution unit comprising a path circuit that is interposed in the path the path for relaying the input power The motor unit for electric power steering as described. 3. The electric power steering unit according to claim 1, wherein the power element substrate includes a metal ceramic substrate having insulation properties and a printed wiring laminated on the metal ceramic substrate. 4. . The electric power steering unit according to claim 3 , wherein the metal ceramic substrate is made of aluminum nitride or alumina. An electric power steering motor unit according to any one of claims 1 to 4, and a gear box for adding the assist torque to a steering torque according to a turning operation of a steering handle. Electric power steering device.

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